JP7085081B1 - Composite member and its manufacturing method - Google Patents

Abstract

An object of the present invention is to provide a composite member in which resins or resins and different materials are composited with high bonding strength and productivity, and a new manufacturing method thereof. An object of the present invention is a composite member formed by joining a first member having a layer made of inorganic particles on a substrate and a second member made of elastoma via a layer made of inorganic particles. The layer made of inorganic particles is a layer having a surface on which inorganic particles having an average particle size of 1 nm or more and less than 20 nm are arranged, and is achieved by a composite member in which at least a part of the surface has a structural color.

Description

The present invention relates to a composite member in which resins or resins and different materials are bonded to each other, and a method for producing the same.

Composite members made by joining resins or resin with different materials such as metal, glass, and inorganic materials have traditionally been used for automobile interior components such as console boxes around instrument panels, engine components, interior components, and digital cameras. It is used for parts that come into contact with the outside world, such as housings, interface connections, and power supply terminals of electronic devices such as mobile phones.

As a method of combining a resin and a resin, or a resin and a different material, a method of forming minute irregularities on the joint surface of the mating member to be joined with the resin and joining by an anchor effect, an adhesive or a double-sided tape. There are a method of adhering using a different material and / or a method of providing a fixing member such as a folded piece or a claw on a resin molded product and fixing the two using this fixing member, a method of joining using a screw or the like. .. Among these, a method of forming minute irregularities on a resin plate or a metal plate or a method of using an adhesive is effective in terms of the degree of freedom in shape for designing a composite molded product (Patent Documents 1 and 2).
In the methods described in these, since a groove is formed on the surface of the target member by a laser, there is local heat generation, and deformation due to thermal expansion of the joined member may occur. Further, when the resin is laser-processed, there is a problem that carbides of the resin may remain on the joint surface and deteriorate the bondability over time.
On the other hand, Patent Document 3 proposes a technique having a layer made of an inorganic material.

International Publication No. WO2014 / 125999 Pamphlet Japanese Unexamined Patent Publication No. 2014-117724 Japanese Unexamined Patent Publication No. 2019-89297

The method described in Patent Document 3 could solve the problems of Patent Documents 1 and 2, but the bonding strength was still insufficient. In addition, there is a problem in terms of productivity because the adhesive strength tends to vary.
An object of the present invention is to provide a new method for manufacturing a composite member in which resins or different materials such as metal, glass, and an inorganic material are composited with high productivity.

The present invention has been achieved by:
1. 1. A composite member formed by joining a first member having a layer made of inorganic particles on a base material and a second member made of elastoma via a layer made of inorganic particles, and the layer made of the inorganic particles is formed. A composite member having a surface on which inorganic particles having an average particle size of 1 nm or more and less than 20 nm are arranged, and at least a part of the surface has a structural color.
2. 2. A method for manufacturing a composite member in which a first member having a layer made of inorganic particles on a substrate and a second member made of elastoma are joined via a layer made of inorganic particles, from the inorganic particles. A method for producing a composite member, wherein the layer is formed by using a dispersion liquid in which inorganic particles having an average particle size of 1 nm or more and less than 20 nm are dispersed in a solvent at a concentration of 0.1% by mass or more and less than 15% by mass. ..
3. 3. The method for producing a composite member according to the above 2, wherein the substrate is made of a resin or an elastomer.
4. The method for producing a composite member according to 2 or 3 above, wherein the solvent of the dispersion liquid in which the inorganic particles are dispersed is an organic solvent having a boiling point of 100 ° C. or lower.
5. The method for producing a composite member according to any one of 1 to 4, wherein the layer made of inorganic particles on the substrate is formed by an advection accumulation method.
6. The manufacturing method according to any one of 2 to 5, wherein the method of joining the first member and the second member is welding or injection molding.
7. The composite member according to 1 above, wherein the joining of the first member and the second member is welding or injection molding.

INDUSTRIAL APPLICABILITY The present invention can provide a composite member having high joint strength and productivity and a method for manufacturing the same.

It is a perspective view of the 1st member of this invention. It is a perspective view of the composite member embodiment 1. It is a schematic diagram which shows the tensile direction, and the velocity for evaluating the joint strength of the composite member embodiment 1. It is a photograph and SEM photograph after advection accumulation of the 1st member of Example 3. The surface on which the inorganic particles are arranged is cut out for SEM photography, and the surface on which the inorganic particles are arranged has a structural color. It is a photograph and SEM photograph after advection accumulation of the 1st member of Comparative Example 1.

Hereinafter, embodiments of the present invention will be described. The present invention is not limited to the following embodiments.

<Composite member>
One aspect of the method for manufacturing a composite member of the present invention is a composite in which a first member having a layer made of inorganic particles on a substrate and a second member made of elastoma are joined via a layer made of inorganic particles. A method for manufacturing a member, in which a layer composed of the inorganic particles is advected and accumulated by using a dispersion liquid in which inorganic particles having an average particle size of 1 nm or more and less than 20 nm are dispersed at a concentration of 0.1% by mass or more and less than 15% by mass. It is characterized by being formed by the method.

<< First member having a layer made of inorganic particles on the base material >>
The layer made of inorganic particles on the first member of the present invention (hereinafter, also simply referred to as a particle layer) is made of inorganic particles having an average particle size of 1 nm or more and less than 20 nm. The thickness of the layer is preferably 1 to 500 nm. This layer is preferably a layer composed of the most densely packed inorganic particles. The layer made of the inorganic particles is formed by an advection accumulation method or the like using a dispersion liquid dispersed at a concentration of 0.1% by mass or more and less than 15% by mass.

In the particle layer by this method, it is known that particles are accumulated by lateral capillary force to form the densest structure, but the inorganic particles having an average particle size of 1 nm or more and less than 20 nm of the present invention are contained in an average particle size of 1 nm or more and less than 20 nm by 0.1% by mass or more. It is presumed that this densely packed structure is more prominently formed when a dispersion dispersed at a concentration of less than 15% by mass is used.

By visually observing the surface on which the inorganic particles of the present invention are arranged, it can be seen that they have a structural color. The range in which this structural color can be observed is most preferably the entire surface on which the inorganic particles are arranged, but is preferably 5% or more, more preferably 20% or more, and particularly preferably 50% or more of the arranged surface.

In Patent Document 3, a dispersion having an average particle size of 25 nm and a concentration of 15% by mass is used. Compared to this case, by setting the range of the present invention, a remarkable increase in bonding strength can be observed suddenly. can.

Unfortunately, it is not possible to directly observe the difference in the fine structure of the layer with an electron microscope or the like, but the surface on which the inorganic particles are arranged has a structural color. Within the scope of the present invention, and with respect to the bonding strength, effects that cannot be explained by continuous changes from Patent Document 3 are exhibited.

As the inorganic particles, ordinary inorganic particles such as silica particles, titanium particles, and alumina particles, metal particles, and metal oxide particles can be applied. The average particle size is preferably 1 nm or more and less than 20 nm, and more preferably 3 to 15 nm. The thickness of the layer made of inorganic particles is preferably 1 to 1500 nm, more preferably 10 to 300 nm, still more preferably 20 to 100 nm.

The layer made of the inorganic particles of the present invention is preferably close-packed. When all the inorganic particles are spherical with the same size, the volume filling factor at the time of close packing is theoretically about 74%, but in reality, the shape of the inorganic particles usually varies to some extent.

Further, even when the inorganic particles are laminated in the thickness direction, the influence of the filling state of the inorganic particles on the outermost layer is considered to be large when considering the bonding with the second member. The close-packing means that the area filling rate of the inorganic particles in the outermost layer of the layer composed of the inorganic particles is 80% or more, more preferably 85% or more.

The average particle size of the inorganic particles was determined by the BET method as follows.
[Average particle size (specific surface area diameter)]
b After drying the inorganic particles dispersed in the organic solvent, the specific surface area S (m ² / g) was measured by the BET method, and the average particle size d (nm) was determined by the following conversion formula (1).
[Number 1]
d (nm) = 6000 / [ρ (g / cm ³ ) × S (m ² / g)] (1)
(In the formula, d represents the average particle size, ρ represents the density, and S represents the specific surface area. For silica, the density is 2.2 (g / cm ³ ).)

The thickness of the layer consisting of inorganic particles was measured by a transmission electron microscope (TEM). Specifically, the diameters of 10 randomly selected inorganic particles were measured on an image of the surface of the inorganic particle layer formed on the substrate by TEM, and the average particle size was obtained. Similarly, the inorganic particles were obtained. The average value of the thickness of the layer measured at five random points on the image of the cross section of the particle layer taken by TEM was taken as the thickness of the layer composed of inorganic particles.

Further, whether or not the packing is the closest packing is generally determined by photographing an arbitrary region (1 μm × 1 μm) on the surface of the base material on which the inorganic particle layer is formed by TEM and observing the packed state of the inorganic particles on the outermost layer. can do.

≪Base material≫
The base material for forming the particle layer of the present invention is not limited as long as it is a base material made of a material to which the advection accumulation method can be applied. For example, metal, glass, ceramic, resin, etc. may be mentioned, but in order to uniformly form a close-packed structure with stronger bonding force, the material must have a thermal conductivity of 500 W / m · K or less. Is preferable, and it is more preferable that the material is 400 W / m · K or less. The thermal conductivity of the base material is preferably in this range from the viewpoint of the solidification rate of the resin during injection molding and welding.

Examples of the resin include ordinary cyclic polyolefin (COC), polyacetal (POM), polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyphenylene sulfide (PPS), polyether ether ketone (PEEK), and liquid crystal resin (LCP). Is a preferred thermoplastic resin, and in particular, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyphenylene sulfide (PPS), and liquid crystal resin (LCP) are preferably used. The thermal conductivity of these resins is 1.0 W / m · K or less.

Examples of the ceramic include alumina, mullite, ferrite, barium titanate, lead zirconate titanate, forsterite, steatite, cordierite, zircon, zirconia, aluminum nitride, silicon nitride, and silicon carbide. These thermal conductivitys are 0.5 to 200 W / m · K. Examples of the metal include aluminum, stainless steel, magnesium, copper, titanium and the like. These thermal conductivitys are 10 to 400 W / m · K.

<< Substrate with surface roughness Rmax ≥ Rz ≥ Rmax -10% and Rmax = 1-10 μm >>
The surface roughness of the surface of the base material forming the particle layer of the present invention is preferably Rmax ≧ Rz ≧ Rmax -10% and Rmax = 1 to 10 μm. A more preferable Rz is Rz ≧ Rmax − 5%. Further, Rmax is more preferably 1.5 to 8 μm, further preferably 2 to 5 μm. With such surface roughness, the filling property of the inorganic particles can be improved.

In order to obtain such a surface roughness, when producing the base material, a molding die suitable for the required surface roughness should be used, the surface of the base material after production should be polished, and the surface of the base material should be plasma. , Treatment with active species such as ultraviolet rays, corona discharge, or physically and / or chemically forming and / or removing irregularities on the surface of the substrate, and containing particles that cause irregularities on the substrate. It can be adjusted by such as.

≪Second member consisting of elastomer≫
The second member of the present invention is made of an elastomer. The elastomer is preferably a resin composition containing an elastomer and an elastomer in which the shrinkage rate sh (%) and the elastic modulus E (MPa) satisfy the relationship of E ≦ 100,000 × exp (-2.64 × sh). .. As the base material resin of the resin composition containing the elastomer, the resin mentioned as the base material of the first member can be used.

As a resin composition containing an inorganic filler, an elastoma, etc. in the preferable resin mentioned as the base material of the first member, an olefin resin composition, an acrylic resin composition, a polyester resin composition, a polyacetal resin composition, a PPS resin, etc. A composition or the like is also preferable as the second member.

Examples of the inorganic filler include fibrous, plate-like, granular, and powder-like inorganic fillers such as glass fibers, glass beads, glass flakes, talc, mica, and silica, and in particular, an inorganic particle layer formed on the first member. When an inorganic filler having the same quality as the inorganic substance used in the above is contained, it is preferable in that the affinity between the inorganic particle layer of the first member and the second member is excellent.

Further, an inorganic filler having a particle size of 0.1 to 50 μm may be contained. It is preferable to include an inorganic filler having an aspect ratio of 1 to 3. As for the content of the inorganic filler, it is preferable that the resin composition constituting the second member contains 5 to 50% by mass of the above-mentioned inorganic filler.

Preferred elastomers include olefin-based polymers such as ethylene-ethyl acrylate copolymers (for example, NUC-6570 manufactured by ENEOS NUC Co., Ltd.), polyester-based elastomers, urethane-based elastomers, and acrylic weights of polymethacrylic acid esters. Examples thereof include coalescence (for example, Zephyac manufactured by Aika Kogyo Co., Ltd., Staphyroid, etc.).

These elastomers can be effectively used even in the form of core-shell particles as long as they can be mixed with the composition of the present invention. Examples of the elastomer of the core-shell particles include Paraloid EXL2311 and EXL2314 manufactured by Dow Chemical Co., Ltd.

The elastoma preferably contains a glycidyl group, and the glycidyl group-containing elastoma is a glycidyl group-containing olefin-based copolymer such as an ethylene-glycidyl methacrylate copolymer or an ethylene-glycidyl methacrylate-methyl acrylate copolymer. (For example, Bond First manufactured by Sumitomo Chemical Co., Ltd.) can be mentioned.

When an elastomer is used as the resin composition in the second member, the content of the elastomer may be 1 to 99% by mass in the resin composition constituting the second member, or 1 to 30% by mass. May be. When the elastomer is an elastomer containing a glycidyl group, the content of the glycidyl group is preferably 0.01 to 20% by mass in the resin composition constituting the second member.

These elastomers may be used as a resin composition constituting the second member in a state of being contained as an additive in the above-mentioned resin, or the elastomer itself or the elastomer may be contained with an additive such as an inorganic filler. May be used as the resin composition constituting the second member.

In the present invention, the reason why the second member made of the resin composition having the above-mentioned characteristics exerts a strong bonding force is estimated as follows. The particle layer on the first member is first exhibited by forming the adhesive force with the substrate so as to have the closest structure by the advection accumulation method. A resin composition having a shrinkage coefficient and an elastic modulus satisfying the above formula is observed to have excellent bonding force with respect to the surface shape of the particle layer of the close-packed structure and as a result of the large surface area of the close-packed structure. ..

In the present invention, the "shrinkage rate sh (%)" refers to a mold having a side gate having a width of 4 mm and a thickness of 2 mm, in which a flat plate-shaped test piece of 80 mm × 80 mm × 2 mm is provided in the center of one side. When the resin composition constituting the second member is injection-molded under the same molding conditions as the molding conditions of the second member when actually manufacturing the composite member, the molding shrinkage in the direction perpendicular to the flow (molding shrinkage) ( Using a flat plate-shaped test piece that has been allowed to stand at 23 ° C. and 50% RH for 24 hours or more after molding, the dimensions of the molded product in the direction perpendicular to the flow of the molded product at a position 20 mm from the end on the opposite gate side (the side on the flow end side). (Width of flat plate-shaped test piece) is measured, and the difference (shrinkage amount) from the mold size corresponding to the position is divided by the mold size), and "elasticity E (MPa)" is , ISO 178 shall refer to the bending elasticity measured in accordance with ISO 178.

<Manufacturing method of composite member>
≪Manufacturing method of the first member≫
In the present invention, when the base material is a resin, the base material is a dispersion liquid in which the inorganic particles constituting the surface layer of the base material are dispersed in a solvent such as isopropyl alcohol, methanol, ethyl acetate, benzene, methyl ethyl ketone and cyclohexane. By immersing the material and pulling it up, it is possible to manufacture the first member in which the inorganic particle layer is formed on the surface of the base material by the so-called transfer accumulation method.

The surface on which the inorganic particle layer is arranged emits a structural color. The structural color can be visually observed as shown in FIG. The dark and light parts have different structural colors and look like a rainbow as a whole. These structural colors are presumed to be colors in which white light (visible light) such as sunlight is scattered, diffracted, interfered, etc. by the inorganic particle layer according to Bragg conditions, and is the inorganic color of the present invention. The particle layer does not always have the same structure, and has various colors that differ depending on the observation angle.

The solvent of the present invention preferably has a boiling point of 40 ° C. or higher and 100 ° C. or lower, and preferably an organic solvent having a boiling point of 50 ° C. or higher and 90 ° C. or lower in order to form a layer having a uniform thickness.
From the viewpoint of handling inorganic particles due to solvent volatilization during translocation and accumulation, the boiling point is preferably room temperature or higher, and from the viewpoint of aggregation and crystallization of inorganic particles in the time until the solvent volatilizes, the boiling point is 100 ° C. or lower. It is preferable to have.

When a metal or ceramic is used for the first member, a solvent such as water is suitable, and when an organic substance such as a resin is used for the first member, an organic solvent is preferable. From the viewpoint of wettability with the base material, the surface tension value of the solvent used is preferably about the same as that of the base material, for example, about 10 to 30 mN / m, more preferably about 15 to 25 mN / m.

The content of the inorganic particles in the dispersion liquid is a concentration of 0.1% by mass or more and less than 15% by mass, preferably 0.5 to 10% by mass, and particularly preferably 1 to 5% by mass. By reducing the concentration, the area having the structural color can be increased, and an increase in the bonding strength can be observed critically.

However, if it is possible to form a layer in which inorganic particles are densely arranged on the surface of the base material, the method is not limited to the advection accumulation method, and various thin film forming methods such as application by brush or spray and spin coating should be used. You can also. Here, when forming the inorganic particle layer, the applied liquid is wiped off or the base material is masked in advance, if necessary, except for the parts used for joining with the second member. By setting it, the inorganic particle layer may not be provided. The number of times of application may be a plurality of times.

When a resin is used as the base material, a resin molded product as the base material may be produced by a commonly used method such as injection molding or extrusion molding. Similarly, if it is glass, a ceramic such as a float method or a down draw method may be used. If this is the case, those produced by a commonly used method such as a normal pressure sintering method or a reaction sintering method can be used. As these base materials, those which have been appropriately processed such as cutting or welding may be used according to the requirements such as designability, functionality, and fixing with other members.

≪How to join the second member≫
In the present invention, the resin composition constituting the second member is brought into contact with the inorganic particle layer of the first member in a molten state, and then the resin composition is cooled and solidified to join the second member. I do. The joining method is not particularly limited, and for example, the first member having an inorganic particle layer is placed in a mold for molding the second member, and the resin composition constituting the second member is used as the inorganic particles of the first member. The second member can be joined by injection molding (so-called insert molding) on the layer, or the region of the surface of the second member that has been molded in advance is heated and melted. Then, the bonding can be performed by contacting with the inorganic particle layer of the first member and pressurizing (so-called welding).

The conditions for insert molding and welding of the second member are not particularly limited, and can be appropriately set according to the type of resin contained in the resin composition constituting the second member.

For example, when the second member is an ethylene-ethyl acrylate copolymer having an elastomer, the cylinder temperature during insert molding is 130 to 200 ° C, preferably 180 ° C or higher, and the injection speed is 5 to 80 mm / s. The holding pressure is preferably 20 to 50 mm / s, and the holding pressure is 5 MPa to 100 MPa, preferably 10 to 50 MPa.

In addition, in the case of insert molding, the formation of the second member and the joining with the first member can be performed at the same time, which is advantageous in terms of process simplification. Further, when the rigidity and toughness of the first member are low and the first member is deformed or damaged by the resin pressure in insert molding, if the first member is joined by welding, the degree of freedom in setting the pressurizing condition is high. , It is advantageous because it is easy to suppress deformation and breakage of the first member.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. Unless otherwise specified, the evaluation was performed in a measurement room at 23 ° C. and 50% RH.

[Evaluation of joint strength]
<Preparation of base material>
POM resin composition 1: Polyacetal resin composition manufactured by Polyplastics Co., Ltd .: Duracon (registered trademark) M90-40, (shrinkage rate 2.0%, elastic modulus 2500 MPa), cylinder temperature 200 ° C., mold temperature 80 ° C., The substrate was injection molded at an injection speed of 50 mm / sec and a holding pressure of 60 MPa.

<Manufacturing of the first member (formation of inorganic particle layer)>
Silica particles having an average particle size of 12 nm in isopropyl alcohol (IPA, surface tension value 20.8 mN / m) or methanol (MTA, surface tension value 22.6 mN / m) were prepared in a liquid adjusted to the concentrations shown in the table. By immersing the above-mentioned base material and then pulling it up so that the joint surface of the step is perpendicular to the liquid surface (dip), silica particles are applied to the joint surface of the base material by the transfer accumulation method. , The first member was manufactured by drying at 23 ° C. to volatilize isopropyl alcohol and forming an inorganic particle layer on the surface of the base material.
For comparison, an average particle size of 25 nm and an average particle size of 45 nm of the inorganic particles were used.

<Manufacturing of composite member (joining with second member)>
Inside a mold for forming a composite member, which is designed so that a part of the inorganic particle layer forming surface of the first member and a part of the cavity of the test piece for forming the second member overlap. A composite member as shown in FIG. 2 was manufactured by insert molding by installing the first member and injection molding the resin composition constituting the second member.

As a second member, an ethylene-ethyl acrylate copolymer: "NUC-6570" (shrinkage rate 3%, elastic modulus 20 MPa) manufactured by ENEOS NUC Co., Ltd. is used at a cylinder temperature of 200 ° C., a mold temperature of 40 ° C., and an injection speed of 10 mm / sec. The second member was injection-molded at a holding pressure of 10 MPa. In addition, a sample in which the cylinder temperature, injection speed, and holding pressure, which are injection molding conditions, were changed was also prepared (Example 2). The results are shown in Table 3.

<Evaluation of joint strength>
With respect to the composite member adjusted by the above method with the combination of the first member and the second member, first, burrs around the contact surface between the first member and the second member are removed, and then a jig for fixing the test piece is used. The first member was fixed to the. Next, using an auto grab AG-20kNXDplus manufactured by Shimadzu Corporation, the bonding strength (MPa) when the first member and the second member were peeled off was measured at a tensile speed of 500 mm / min. Tables 1 to 3 show the results of changing the injection conditions of the second member.

[Productivity evaluation]
<Good product rate>
The composite member was insert-molded with 10 shots, and the first member and the second member did not peel off at the time of mold release, and the sample was counted as the number of non-defective products, and the non-defective product ratio was calculated (for example, 3 out of 10). If it can be collected without peeling, 3/10 x 100 = 30%.). The results are shown in Tables 1 to 3.

As shown in Tables 1 to 3, it can be seen that the bonding strength is specifically improved within the scope of the present invention.

FIGS. 4 and 5 show photographs of test pieces obtained by treating silica particles having an average particle size of 12 μm by an advection accumulation method. FIG. 4 is an SEM image showing the deposition arrangement of silica particles in the isopropyl alcohol 5% concentration solution and FIG. 5 is the isopropyl alcohol 30% concentration solution.

According to this, in the 5% concentration solution, the structural color is observed in the area of about 60% where the inorganic particles on the surface of the test piece are arranged, and it can be seen that a uniform inorganic particle layer is formed. In the 30% concentration solution, no structural color is observed, and further precipitation of crystals of 10 to 50 μm is observed. No structural color is observed in the samples with average particle sizes of 25 nm and 45 nm.

Claims (7)

A composite member formed by joining a first member having a layer made of inorganic particles on a base material and a second member made of elastoma via a layer made of inorganic particles, and the layer made of the inorganic particles is formed. , A layer having a surface on which inorganic particles having an average particle size of 1 nm or more and less than 20 nm are arranged, and at least a part of the surface has a structural color developed by the arrangement of the inorganic particles . A first member having a layer made of inorganic particles on a base material and a second member made of elastoma are joined via a layer made of inorganic particles, and the layer made of the inorganic particles has an average particle size. It is a layer having a surface on which inorganic particles of 1 nm or more and less than 20 nm are arranged, and at least a part of the surface is a method for producing a composite member having a structural color expressed by the arrangement of the inorganic particles, and is composed of the inorganic particles. A method for producing a composite member, wherein the layer is formed by using a dispersion liquid in which inorganic particles having an average particle size of 1 nm or more and less than 20 nm are dispersed in a solvent at a concentration of 0.1% by mass or more and less than 15% by mass. .. The method for manufacturing a composite member according to claim 2, wherein the substrate is made of resin or elastomer. The method for producing a composite member according to claim 2 or 3, wherein the solvent of the dispersion liquid in which the inorganic particles are dispersed is an organic solvent having a boiling point of 100 ° C. or lower. The method for manufacturing a composite member according to any one of claims 2 to 4, wherein the layer made of inorganic particles on the substrate is formed by an advection accumulation method. The manufacturing method according to any one of claims 2 to 5, wherein the method of joining the first member and the second member is welding or injection molding. The composite member according to claim 1, wherein the joining of the first member and the second member is welding or injection molding.

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